Pugh, D. S.
Buku Teks
Ritchie, J.B., author
West Publshing Company, 1980
Buku Teks
edited by Mason Haire
John Wiley & Sons, 1959
Buku Teks
Hatch, Mary Jo.
Oxford University Press , 2013
Buku Teks
Thompson, James D., author
McGraw-Hill, 1967
Buku Teks